In law enforcement and military environments it is often necessary and appropriate to use protective shields of various forms and configurations to protect personnel and equipment from injury or mechanical damage caused by projectiles including bullets, spall, shrapnel, etc. The shielding apparatus may be of a type that is worn as protective personnel body armor; a type that is used to provide protective panels for a land, sea or air vehicle; a type that may be configured to provide a shelter; or merely a collection of panels that can be affixed to a wall of a shelter to prevent penetration thereof. In these applications, it is usually desirable that the shielding apparatus be made of material that is strong, light and thin; and in the case of body armor, it should also be capable of dispersing or otherwise dealing with body heat and perspiration.
While means for opposing a particular type of ballistic threat can usually be designed and/or configured for inclusion in original equipment, the provision of easily retro-fittable and/or transportable armor materials is more difficult in that it must usually have characteristics such as formability, relative lightness in weight, durability in hostile environments, and other particular attributes such as having the capability of deflecting or capturing incoming projectiles.
Bullet-proof vests are a form of personal body armor that either deflects or absorbs the impact of gun-fired projectiles and explosive fragments fired at the torso of its wearer. Soft vests made from layers of tightly-woven fibers are intended to protect the wearer from projectiles fired from handguns, shotguns, and shrapnel from explosives such as hand grenades and improvised explosive devices (IUDs). Soft vests are usually made of flexible aramid fibers and have long been worn by police forces and private security guards.
Soft vests per se do not protect the wearer by deflecting bullets. Instead, the layers of high tensile strength material forming the vest are intended to catch the projectile and spread its force over a larger portion of the wear's body, and hopefully bring the projectile to a stop before it can penetrate into the body. This tends to deform the bullet, further reducing its ability to penetrate. However, while a vest can prevent invasive bullet wounds, the wearer's body must still absorb the bullet's energy, and can often incur blunt force trauma in which a majority of users experience only bruising; but impacts can still cause severe internal injuries.
Another problem with soft vests is that they offer little protection against arrows, ice picks, stabbing knife blows, bullets with their points sharpened, and armor-piercing rounds because the striking force is concentrated in a relatively small area and can often push or be pushed through the weave of bullet-resistant fabrics. Accordingly, vests designed specifically to protect against bladed weapons and sharp objects are used by prison guards and other law enforcement officers.
Also, since soft body armor vests are usually ineffective against most military rifle rounds, some such vests may be augmented with metal, ceramic or polyethylene plates that are carried in pockets included in the vest to provide extra protection to vital areas. Hard-plate carrying vests are worn by armed response police forces as well as combat soldiers in the armies of various nations. These plate carrying vests have proven effective against bullets fired from most handguns and a range of rifles, and have become standard in military use.
However, these plated vests still have shortcomings because the energy of large fragments or high velocity bullets hitting some types of plates can still cause life-threatening, blunt trauma injuries. In an attempt to solve this problem, heavier ceramic and steel armor plates have been added to stop rifle caliber rounds. Unfortunately, because of the weight, such vests are often discarded and the soldier is left unprotected. In addition, since the plates often merely deflect the projectile or its resulting spall, it is not unusual for a wearer to survive the initial impact only to receive substantial and even lift threatening injury as the deflected material strikes another part of his body. For example, many plated vest wearers have received devastating injury to their face, arms or head as a result of bullet spall deflected from the surface of a vest carried hard armor plate.
As protective personnel armor of various types and configurations has evolved, attempts at developing thin, light, less insulating, flexible and breathable protective materials have been made in order to create garments that are more wearable by the user. However, to maintain a level of protection in soft vests against higher caliber pistols and firearms it is still necessary that many layers of ballistic resistant fabric be used in combination with some type of rigid metallic or ceramic insert. Unfortunately, this increases the overall weight and thickness of the garment and reduces its flexibility.
It is recognized as desirable that a protective body armor garment cover as much of the wearer's body as possible while at the same time maintaining wear-ability. Thus, the thinner and lighter the protective article, the more feasible it is to increase body coverage. Moreover, conceal-ability of the anti-ballistic body armor can be improved if it can be constructed to be thin and non-bulky. Thin and lightweight armor can also allow increased mobility so that those wearing the article are not hampered from doing their job.
In the last few decades, several new fibers and construction methods for bulletproof fabric have been developed including woven Dyneema, GoldFlex, Spectra, Twaron, and Zylon. Although Kevlar has long been used, some of the newer materials are said to be lighter, thinner and more resistant than Kevlar, but are considerably more expensive. But even so, the expense is justified because the more lightweight, thin and less insulating a protective ballistic resistant garment is made, the more likely an intended user (such as a law enforcement officer or military personnel) will actually wear the garment, especially in the case of hostile environmental conditions and long working shifts.
Reduction of weight and improvements in thinness of materials have been made by the utilization of stitched together layers of sheets of these woven materials. For example, high tensile strength aramid fibers such as Kevlar® have often been employed in forming the woven ballistic fabric. Other aramids such as Twaron.®T-1000 and Twaron.®T-2000 have also been used in forming woven sheets of material used in ballistic resistant pads. Dyneema and Spectra are synthetic fibers based on ultra high molecular weight polyethylene which has yield strengths as high as 2.4 GPa and density as low as 0.97 Kg/l (for Dyneema SK75). This gives a strength/weight ratio as much as 15 times stronger than steel and up to 40% stronger than Aramids.
In the case of body armor, various voluntary governmental ballistic standards have been established to certify certain ballistic resistant garments. The tests determine the ability of the garment to resist penetration from various ballistic rounds shot from various types of weapons. In particular, the National Institute of Justice (NIJ) Standard 0101.03 certification tests are frequently used in testing certain body armor products. These tests are grouped into different threat levels, with each threat level corresponding to ballistic projectile penetration stopping capabilities of various ballistic rounds fired from designated weapons. For generally concealable type ballistic resistant body armor, NIJ Standard certification tests are often performed for NIJ Threat Levels IIA, II and IIIA. Threat Level IIIA is a higher standard level than Threat Level II which in turn is a higher standard level than Threat Level IIA.
There is thus a continuing need to provide improved armor materials that are thin and lightweight, have the ability to capture rather than reflect projectiles, bullet spall and the like, and in the case of body armor have good insulating and/or heat application or removal properties to increase their wearability while still meeting industry standards for armor materials.